Coloradans have been social distancing to various degrees for about three weeks now in an attempt to slow the spread of the novel coronavirus. For such an active, adventure-loving population, those three weeks have probably felt more like three years. And at this point, we’re all likely wondering: Are these social distancing measures actually working?
According to Gov. Jared Polis, the answer is yes.
During an address to the state on Monday, April 6, Polis explained that the rate at which the virus is doubling has slowed since early social distancing measures were put into place. At the beginning of the outbreak, the number of positive cases was doubling approximately every 1.5 to two days. That rate has since slowed to about every six or seven days, Polis said.
“This is a remarkable achievement by you, the people of the state,” he said. “You’re truly helping to turn the tide against this deadly virus. We need to keep up the good work for awhile longer so we can eventually return to a level of normalcy in our economy and society.” To ensure that Colorado is able to stop the virus’ spread and keep the health care system from being overwhelmed, Polis extended the statewide stay-at-home order, which was originally set to expire on April 11, until April 26—four days sooner than federal recommendations. “If there is any way to safely end it sooner, I will,” Polis said. “And likewise if Coloradans aren’t staying at home and the numbers of the dead and dying continue to pile up, it could go longer.”
This announcement about the virus’ slowed doubling rate is, of course, good news. It means that the virus will now peak at a later date, which gives Colorado more time to acquire life-saving ventilators, hospital beds, and protective medical gear. Such progress, Polis has repeatedly explained, reflects the impact of early social distancing measures, including school closures, prohibitions of gatherings of 10 or more, and the shuttering of bars and restaurants.
It takes about 12 days from the time a social distancing measure is enacted to when we might see its impact, and as such, Polis’ address on Monday evening is the first look at the effect of Colorado’s stay-at-home order, which was instituted on March 26. The 12-day lag time is because it takes, on average, about four to five days after initial exposure to COVID-19 for someone to develop symptoms, and another eight days, on average, for that positive case to be reported to the state.
“It will take a few weeks before we have a better sense of how significantly the stay-at-home order has slowed the spread of COVID-19,” a spokesperson with the Colorado Department of Public Health and Environment (CDPHE) said via email last Thursday, April 2. “We are seeing indications that many Coloradans are complying with the order, but everyone must comply, and only go out for essential needs. If we work together to slow the spread, it will save thousands of lives.”
To better grasp how social distancing measures are potentially impacting the spread of the virus in Colorado, it helps to understand the concept of R naught. Polis first discussed the term, which represents the number of people that one person with COVID-19 is likely to infect, in a press conference on Friday, March 27. Before social distancing measures were introduced in Colorado, the R naught value was between three and four, Polis said. Assuming an R naught value of three means that every sick person was infecting three new people, which was then leading to nine new infections, then 27, then 81, and so on. Assuming an R naught between three or four meant that the virus was growing at an exponential rate. And if cases continued doubling every 1.5 to two days, the virus could have eventually killed between 30,000 and 50,000 Coloradans, Polis said on March 30.
To better grasp how social distancing measures are potentially impacting the spread of the virus in Colorado, it helps to understand the concept of R naught. Polis first discussed the term, which represents the number of people that one person with COVID-19 is likely to infect, in a press conference on Friday, March 27. Before social distancing measures were introduced in Colorado, the R naught value was thought to be between three and four, Polis said. But according to new data, that initial R naught value was likely between 2.5 and 3.5. Assuming an R naught value of three means that every sick person was infecting three new people, which was then leading to nine new infections, then 27, then 81, and so on. And if cases continued doubling every 1.5 to two days, the virus could have eventually killed between 30,000 and 50,000 Coloradans, Polis said on March 30.
With the social distancing measures that are currently in place, “we’re trying to knock that number [R naught] down as hard as we can,” the governor said in a press conference on Wednesday, April 1. “We have to get that number below one for the virus to start to die out.”
We don’t currently know the value for R naught, Katie Colborn, assistant professor of surgery at the University of Colorado School of Medicine and assistant professor of biostatistics and informatics in the Colorado School of Public Health, told 5280 on Thursday, April 2. Colborn is on a team of folks from local universities working on COVID-19 modeling for the governor’s office, and said more data will likely be available this week.
But based on recent traffic reports, Coloradans have likely reduced social contact by 60 percent, Polis said on March 30. Newer data by Colborn’s team suggests initial social distancing measures only reduced social contact by about 45 percent. Either way, more reduction is needed. COVID-19 is “still an extremely contagious virus,” Polis warned, and the hope is that the reduction in social contact will be “more in the 70 to 80 percent range.”
“We fully expect that these additional separation measures, as long as people are following them, will also show reduced spread of the virus in Colorado and help us all return to be able to support ourselves, and lessen the need for more extensive measures over a greater period of time,” Polis said.
There are some caveats with the data released so far. First, it’s based only on the number of confirmed positive cases and not the number of people who actually have the virus. “We’ve ramped up testing but we know that there’s plenty of people who have been infected and haven’t been tested for it,” Polis said during his March 30 press conference. On April 3, he announced that the state was currently testing 2,000 people per day (up from 160 a month ago), and that by May 1, the goal is to test at least 5,000 people a day.
A better way to evaluate the virus’s actual reach is to look at the number of hospitalizations, said Colborn. Based on current estimates by Colborn’s team, about 4.4 percent of all people who are infected with COVID-19 might need to be hospitalized. With that logic, if you divide the number of hospitalizations by 0.044, “you can get kind of a ballpark estimate of how many infections we really might have,” she explained. That means about 24,522 people in Colorado might be infected with COVID-19—more than four times as many as is currently reported by CDPHE, according to the state’s latest data as of Tuesday night.
During Polis’s address to the state on April 6, he said that between 10 and 20 percent of people who contract the virus will need hospitalized care; when asked about the discrepancy is hospitalization rates, Colborn said perhaps the governor’s calcuation represents the number of symptomatic people that require hospitalization; by contrast, the 4.4 percent calculation represents the total number of infected people—both symptomatic and asymptomatic—that require hospitalized care. When contacted about this discrepancy, a CDPHE spokesperson said via email that they believe the governor was referencing the hospitalization rate for adults 60+ or another adult age group. In the 60+ age group, the hospitalization rate is about 20 percent for symptomatic individuals, the spokesperson said.
As we track the virus in Colorado, Colborn said it’s more important to watch the number of hospitalizations versus the number of confirmed cases. Based on a graph Colborn shared with 5280 last Thursday but asked that it not be published because she did not have those permissions, the rate of new hospitalizations is currently holding fairly steady, rather than increasing, “which is what would be expected under no interventions,” she explained. And in recent days, the rate even seems to be declining—another good indicator that what we’re doing is likely having an impact. (Though as Polis reiterated during his press conference on April 3, there is a lag time between when a measure is taken and when the impact of that measure could be notable—for hospitalizations, that lag time is about 15 days.)
Still, Colborn was hesitant to make a definitive connection between the social distancing steps taken so far and the decreased doubling rate of the virus. “Random things can happen that we can’t measure, and you can falsely attribute those to interventions,” she said.
Uncertainty aside, Colborn had positive, hopeful words for anxious Coloradans.
“It’s hard right now, but I truly believe we’re saving lives and that this isn’t going to go on forever,” she said. “We’re gonna come up with a plan that allows people to go back to work and for kids to go back to school, and it’s not going to be really far down the road.”
And on Monday, April 6, Colborn shared new data that delivered more good news: If Colorado is able to adhere to high levels of social distancing throughout April (in the 70 to 80 percent range that Polis mentioned), we can not only flatten the curve, but bend the curve to the degree that we will see a decline in cases and hospitalizations and hospital capacity will not be exceeded.
Editor’s note, 4/8/20: This article has been updated to reflect new information and data.